Among true artists, there are no secrets. Pooling our knowledge can only make us better, so share the secrets of your success; whether you've got some good writing or drawing tips.
General drawing tips:
Don't be afraid to use an existing picture as a model or a base. But never blatantly rip off someone else's pic.
Black and white can be more effective than colour.
Draw a basic outline and decide where all the body parts and props are going to go before adding detail.
Think about lighting, and where all the shadows will be (bit hypocritical of me; as I'm often too chicken to add shading). If you're good at sculpting, you could make a basic clay model, and position it in various light sources to see where the light hits it and where the shadows go.
Make sure you've got something to lean on and are comfy. I do my best drawings sat on my bed with the warm sunshine pouring softly through my window and a friendly cat nearby.
Consider proportion. A burrowing animal, for example, will not have long, lanky legs. Look at animal drawing carefully to see if it can support its weight, where its centre of gravity is and so forth. Try to imagine it moving.
Pencil drawing tips:
Keep more than one pencil, and keep at least one sharp and at least one blunt. Use the sharp one for fine detail and narrow lines, and use the blunt one for shading; you'll automatically press less hard and you'll get a softer texture.
Erasers: have two. Keep one in an old film canister (or its own plastic holder if you have one of those funky ones), to keep it clean and fresh. Use it when you want to totally obliterate something. Keep another one in a case full of pencils that you use a lot, and in a few weeks it'll become nice and grubby with pencil graphite. Use it when you want to smooth out scribbly lines or blocks of shading. It'll smooth out the graphite on the paper without erasing it.
For highlights, or to show that something is wet, try shading the whole area, and then rubbing out where the highlights will go with your clean rubber.
For fur, once I've drawn the outline, I go over it, but with a slightly jagged/wavy line, then put in individual fur strands along the outline with short, sweeping pencil strokes.
Get a quality sharpener. Some people even sharpen their pencils with craft knives.
Invest in pencils of different hardness grades.
Oil pastel tips: (I love my oil pastels, I do. They can be expensive but they're worth it.)
You can always add more wax, but you can't take it off! Layers, not bulk. Suprisingly, the same goes for
GIMP - whack some colour down with a paintbrush, then use the smudge (which blends colours in an oil-pastlly effect) and blur (which makes outlines hazy) tools to mix it in. You can always add more colour, but it'll take a lot of smudging to work in too much excess.
Use a different finger for smudging each colour.
For large areas of uniform colour or to create a base on which you will alter small areas of colour, colour the area in with coloured pencils first. Do it lightly, though (and add layers, not one huge thick one to start with); oily wax won't take on thick layers of syntheticcy graphite. You can use watercolours as bases, but I don't very often as I can't be bothered to set everything up, wait for the paint to dry and then tidy up afterwards.
Wash your hands when you've finished. :)
General artwork tips:
Keep practicing. Compare my pictures of half a year ago with ones now (well, actually you can't; I deleted from the internet all my old pictures I no longer like), and even though there's only a few months' difference, there's a huge improvement. I love drawing, and I didn't stop.
Everyone has their own style. Keep trying until you find yours (it's ok to borrow bits of other peoples' until you get there).
Draw/write what YOU want. It is better to write/draw for yourself and have no public, than to write/draw for the public and have no self. I have plenty of pictures and pieces of writing that I made purely for my own enjoyment.
Do it again until you're happy with it. If you call it 'finished' even though you don't like it, that's wrong. If you really can't be bothered to work on it any more, discard it or come back to it another day.
Don't compare yourself to others. You'll only make yourself sad if you find someone's work that you think is 'better' than yours. This is not a competition. This is ART. There is no right or wrong way.
Experiment! Pioneer daring new techniques. Try a medium you've never tried before.